Free-diving photographer Tim Calver [see his recent shots for Adventure] can hold his breath long enough to get cool shots a hundred feet [30 meters] underwater. But his tankless technique is just as handy for snorkelers who want more face time with fish a dozen feet [3.5 meters] down.

Relaxationboth mental and physicalis the key, Calver says. Prepare by taking long, meditative breaths, exhaling everything, and then filling your lungs completely. Next, bend at the waist, kick one leg up in the air, and commence a slow, easy flutter kick in a straight line toward the bottom.

"The less effort you use, the more time underwater you'll have without bubbles and noise disturbing the sea life," he says.